textproduct: Rapid City

KEY MESSAGES

- Warm and dry conditions continue this week, with 90s returning to the forecast Thursday and Friday.

- Elevated to near-critical fire weather conditions continue to result; focus remains on Thursday and Friday, although lack of overlap between the lowest humidities and strongest winds support low confidence in meeting Red Flag Warning criteria.

- High confidence in no precipitation until at least Friday evening, if not Saturday evening.

- Next organized storm system remains expected this weekend into Monday, but signal for cooler temperatures slightly moderating.

DISCUSSION

(This Evening Through Wednesday) Issued at 156 PM MDT Wed Sep 9 2026

Our main weather concern this week remains hot, dry, and at times breezy conditions resulting in elevated to near-critical fire weather, with all eyes then turning to this weekend's storm system. The previously noted trend in a quicker arrival to cooler air Friday remains on track, supporting cooler high temperatures in the 70s in the northwest CWA (especially Campbell and Harding counties), ranging up into the upper 80s and lower 90s to the southeast. Forecast confidence is high in no precipitation until at least Friday evening, if not Saturday evening.

Long-range deterministic models continue to key in on two primary features this weekend. The first is a large low pressure center crossing Canada to our north, which will assist in tightening the pressure gradient and increasing northwesterly winds Friday afternoon and evening (gusts 25-40 MPH across the region). This will especially be a fire weather concern...still not expecting Wind Advisory-level winds at this time. Some hint of troughing extending southwestward from this parent low may also help support some isolated shower/thunderstorm potential starting late Friday afternoon into the first part of Friday night, although confidence in this period is low (and NBM-based PoPs are trending a bit lower). Meaningful or widespread QPF is unlikely, if it rains at all. The second primary feature will be another closed low rotating down the back side of this Canadian parent low and then swinging eastward/inland across the northern Rockies. Moisture advecting in on southwest flow ahead of this low, along with increasing upper-level support, will bring us a better chance of more organized precipitation sometime in the Saturday evening/Sunday/Monday timeframe, along with cooler temperatures and increased humidities. Looking at temperatures...the news isn't great for those looking for their first taste of fall, as NBM high temperatures have moderated a bit...generally now holding in the 70s Saturday, Sunday, and Monday (although some high temps as low as the 60s may still be possible up in the Black Hills and across the northwestern South Dakota plains). Overnight lows will reach the 40s. Looking at rainfall...forecast totals currently range from as low as 0.10" across northwest Wyoming, to potentially 0.50-0.75" across the plains of central South Dakota. Continue to keep in mind that our actual eventual temperatures (and QPF amounts) will be tied to the strength and track of this low, and 500mb height cluster analysis continues to highlight some differences/ensemble uncertainty tied to speed and progression of the low (although so far no major trends affecting our forecast). Overall, no deviations were made from NBM and WPC guidance in the forecast from Friday onward at this time.

AVIATION

(For the 00Z TAFS Through 00Z Thursday Evening) Issued At 516 PM MDT Wed Sep 9 2026

VFR conditions through the TAF period.

FIRE WEATHER

Issued At 156 PM MDT Wed Sep 9 2026

We continue to monitor hot, dry, and periodically breezy conditions today through Friday, resulting in elevated to near- critical fire weather. For today, afternoon minimum relative humidity values will range from 12-25 percent...driest across northeast Wyoming...but overlap with critical winds seems limited with most areas gusting 20-25 MPH (slightly stronger across the northwestern South Dakota plains).

Thursday and Friday continue to look somewhat concerning compared to other days this week, but a few nudges and trends in the forecast are noted today precluding any Red Flag Warnings at this time. Thursday...RH values plummet to 6-18 percent and temperatures heat into the 90s, but coverage of wind gusts exceeding 25 MPH is very limited. A few spots may reach that threshold based on the (usually higher) NBM guidance, but other guidance has trended a bit lower, including the HREF mean which keeps gusts below 20 MPH, and evening the HREF ensemble max only brushes 25 MPH in a few spots. Of course, the hot and dry conditions will still do nothing to hinder burning. Very poor overnight RH recovery also remains expected Thursday night into Friday morning (only 20-30 percent from the Black Hills and Fall River County area westward across northeastern Wyoming). Friday...winds really ramp up with gusts reaching 25-40 MPH regionwide, but afternoon RH values have trended slightly higher compared to yesterday's forecast...now only bottoming out at 15 percent (south/NE border) to 30 percent (north/ND and MT border). It remains possible a few zones may eventually need Red Flag Warnings Friday, but confidence is low at this time.

Forecast confidence is high in no precipitation until at least Friday night, if not holding until Saturday evening as our next system approaches. This system still looks to potentially support cooler temperatures and higher humidity starting Saturday, but the potential for wetting rains remains uncertain.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.